A disc drive is a data storage device used to store and retrieve computerized data in a fast and efficient manner. Generally, a disc drive comprises a head/disc assembly (HDA) which houses mechanical portions of the drive and a printed wiring assembly (PWA) which supports electronics used to control the operation of the drive.
The HDA includes a base deck which supports a spindle motor used to rotate one or more rigid discs at a constant high speed. The discs are coated with a nonvolatile medium to which data are magnetically stored and retrieved by an array of transducers ("heads") mounted to a rotary actuator. The heads are supported over the corresponding disc surfaces by air bearings set up by the rotation of the discs and controllably positioned in response to the application of current to an actuator coil which forms a portion of a voice coil motor (VCM).
A processor based, digital servo circuit such as discussed in U.S. Pat. No. 5,262,907 issued to Duffy et al., assigned to the assignee of the present invention, provides closed loop positional control of the heads. Servo data are written to each of the disc surfaces during disc drive manufacturing as a plurality of servo fields which are arranged as radially extending wedges which extend from the inner to the outer diameters of the discs. The servo data define a plurality of concentric tracks on each of the surfaces. User data are stored on the tracks in user data fields (sectors) which are subsequently defined between adjacent servo wedges during a disc drive formatting operation.
The servo circuit provides two main operations: track following, wherein the selected head is maintained over a particular track on the corresponding disc surface, and seeking, wherein currents are applied to initially accelerate and then decelerate the head from an initial track to a destination track on the disc surface. Proper operation of the servo circuit requires accurate detection and processing of the servo data from the disc surfaces.
It is common to provide a preamplifier circuit in proximity to the heads in order to provide preamplification of readback signals transduced by the heads in order to reliably transmit the signals to the disc drive PWA. The readback signals are initially provided to a read/write channel, with the readback signals from the user data fields being reconstructed into the originally supplied data by the host computer. The readback signals from the servo fields are passed from the read/write channel to a demodulator of the servo circuit, which conditions the servo data for use by the servo processor.
To support high volume manufacturing efforts, it is increasingly common for disc drive manufacturers to produce large numbers of nominally identical disc drives which have individually selectable electronic parameters which are adjusted during disc drive manufacturing and field operation to ensure the drive continues to operate at acceptable levels of performance. Examples of such parameters include read and write current levels used by the heads, tap weights and timing values used by the read/write channel, detection thresholds used by the servo circuit, etc. Nevertheless, because of limitations associated with high volume manufacturing environments, the sheer number of parameters available for adaptation makes it economically unfeasible to individually optimize every available parameter in every drive; hence, disc drive manufacturers typically attempt to adapt those parameters which have the greatest impact on the operational performance of the drive and provide default, global settings for remaining parameters.
As disc drives continue to be provided with ever increasing data storage capacities and levels of data transfer rate performance, as well as significantly greater levels of parametric adaptation capabilities, there remains a continued need for ways to efficiently and quickly select optimum parameter values to improve disc drive operational performance. It is to such improvements that the present invention is directed.